The Biology Project: Biochemistry

Large Molecules Problem Set

Problem 10 Tutorial: Protein-protein interactions

Tutorial to help answer the question

Proteins 1 and 2 interact strongly. A significant part of the interaction is between the amino acid side chains shown below.
Protein 1= arginine C6H14N4O2 . Protein 2 = glutamic acid C5H9NO4
Assume that a mutation occurs in protein 2 that changes the amino acid shown above to one of the amino acids shown below.
Protein 2= aspartic acid C4H7NO4 , protein 2= Lysine C6H14N2O Protein 2= serine C3H7NO3 and protein 2= leucine C6H13NO2
What change should disrupt the interaction between proteins 1 and 2 the most? the least?


Attractive force
The arginine amino acid side chain of protein 1 has a positive charge. The glutamic acid amino acid side chain of protein 2 has a negative charge. The most likely interaction between these two amino acids is an ionic bond, i.e. an attractive force between the positive and negative charge.
Most disruptive
If the amino acid of protein 2 were mutated to an amino acid with a positive charge, such as lysine, then the positive charges of the arginine of protein 1 and the lysine of protein 2 would repel each other. Lysine would be the most disruptive to protein-protein interaction.
Least disruptive
If the amino acid of protein 2 were mutated to another amino acid with a negative charge, such as aspartic acid, the positive charge of the arginine of protein 1 and the negative charge of aspartic acid of protein 2 might still form an ionic bond. Aspartic acid would be the least disruptive to protein-protein interaction.

problem 10 Answer Problem 11

Large Molecules Problems BiochemistryVocabulary Biology Project Home Page

The Biology Project
Department of Biochemistry and Molecular Biophysics

The University of Arizona
Revised: February 5, 2003
Contact the Development Team
All contents copyright © 1996-2003.
All rights reserved.